Government regulations and consumer demand have resulted the inclusion of air bags, as secondary restraint systems, in virtually all new automobiles being sold today. The use of air bags in conjunction with seat belts has drastically reduced the number of fatalities related to motor vehicle accidents.
Air bag restraint systems are generally concealed from view during normal operation of a vehicle by arranging the air bag restraint systems behind automotive interior trim articles, such as instruments panels, dashboards, and/or door panels.
In order to provide for rapid deployment of air bags during a collision, the interior trim articles behind which air bags are concealed are often formed of a multi-layered structure that includes a rigid substrate having hidden doors formed therein, an outer decorative skin layer, and a soft cellular polyurethane foam layer formed therebetween. The hidden doors of the rigid substrate are configured and arranged in such a manner that the edges of the doors define discernable patterns, such as patterns in the form of H, C, U and X shapes.
During a collision, at impact the gas generating system of the air bag module is actuated. As the gas inflates the air bag it is directed toward and pushes against the backside of the hidden doors and forces the hidden doors to open into the passenger compartment of the vehicle. The emergence of the hidden doors into the passenger compartment creates a passageway which permits deployment of the air bag into the passenger compartment of the vehicle. The deployed air bag protects the occupants of the vehicle from experiencing serious impact injury.
In order to minimize obstruction of the passageway through which the expanding air bag is deployed, the underside of the outer skin can be provided with structurally weakened tear seams. These tear seams often take the form of perforated or channel-like patterns, and are constructed and arranged to substantially correspond to and overlay the pattern (e.g., H-shape) defined by the edges of the hidden doors of the substrate. During deployment of the air bag, the outer skin tears or fractures along the structurally weakened tear seams. Absent the presence of such structurally weakened tear seams in the outer skin, the outer skin may possess sufficient internal strength to resist fracture upon deployment of the air bag. If the skin does not fracture, the entire outer skin can become separated from the underlying rigid substrate and/or the multi-layered structure can become detached from the vehicle frame and imperil the safety of the vehicle occupants.
Different techniques have been proposed for forming multi-layered interior trim panels having outer skins that are provided with structurally weakened, rupturable tear seams. The use of knifes and lasers to cut or score inside portions of cover layers or skins has been used by some manufacturers. These methods require precise control of the depth of the cut and can result in a significant number of rejected parts when there are variations in the depth of the cuts.
Another proposed method for forming invisible tear seams in interior trim panels involves embedding seam-defining structures within the cover layers or skins. The seam-defining structures can be strips of film or pieces of string or twine. One disadvantage with this method is that if the embedded seam-defining structures are not properly positioned they can appear as an unsightly defect on the outer surface of the interior panels.
The present invention provides a method for making interior trim articles having tear seams formed therein which method involves spray forming tear seams in a precise repeatable manner.